Assuming the arrays are called @a1, @a2, @a3, the following ought to work (although I didn't test it). It should work correctly even if a value appears twice in a single array. This technique is trivially adaptable for different number of arrays, or different counts. 
my @twice = do {
    my %a;
    map {my $a = $_; map {$a{$_}{$a}++} @$a} \@a1, \@a2, \@a3;
    grep {2 == keys %{$a{$_}}} keys %a;
};

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In reply to Re: array comparison question by Anonymous Monk
in thread array comparison question by Anonymous Monk

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